The present invention relates to a cable reel having a belt-like cable such as a flat cable utilized for electrical connection between a fixed member and a movable member.
FIGS. 6 and 7 are an exploded perspective view and a horizontal sectional view of a conventional cable reel, respectively.
Referring to FIGS. 6 and 7, reference numeral 1 designates a movable member having a central cylindrical portion 1a extending downwardly. A holder 2 forming an inner ring wall is fixed to the outer circumference of the cylindrical portion 1a. The holder 2 has an axial slit 2a. Reference numeral 3 designates a flat cable formed by laminating a plurality of conductors between a pair of base films. The flat cable 3 is wound with a plurality of turns. An inner circumferential end portion of the flat cable 3 is inserted through the slit 2a, and is folded at right angles between the holder 2 and the cylindrical portion 1a, then led through a cable leading member 4 fixed to the movable member 1 to the outside of the cable reel. The inner circumferential end of the flat cable 3 is divided into two portions to which connectors 5a and 5b are mounted.
Reference numeral 6 designates a fixed member having a central hole 7. The fixed member 6 engages in a snap fashion with a lower end of the cylindrical portion 1a of the movable member 1. Thus, the movable member 1 is rotatably engaged with the fixed member 6. The fixed member 6 has at its outer circumference an outer ring wall 8. When the movable member 1 and the fixed member 6 are assembled, there is defined an annular space between the outer ring wall 8 of the fixed member 6 and the inner ring wall 2 of the movable member 1 for receiving the flat cable 3. A cable guide 9 projects obliquely downwardly from the outer ring wall 8 for guiding and leading an outer circumferential end portion of the flat cable 3 to the outside of the cable reel. A connector 10 is mounted to the outer circumferential end of the flat cable 3 led out of the cable reel.
A ring-like fixing member 11 is mounted on the upper end of the outer ring wall 8 so as to fix the outer circumferential end portion of the flat cable 3 to the fixed member 6. The fixing member 11 has a downward projection 12 for guiding the flat cable 3 in cooperation with the cable guide 9 of the fixed member 6 in such a manner that the flat cable 3 is sandwiched between the projection 12 and the cable guide 9. The fixing member 11 has a cutter 13 having a knife-like edge on the inner side of the projection 12. The outer circumferential end portion of the flat cable 3 is folded at a portion 3a at right angles, and a folded line of the portion 3a is positioned facing the knife-like edge of the cutter 13 as shown in FIG. 7. The cable 3 is then led out between the cable guide 9 and the projection 12.
The cable reel thus constructed is actually used in such a manner that the cylindrical portion 1a of the movable member 1 is inserted and fixed to a steering shaft as a rotating member of a steering device for an automobile, for example, and the fixed member 6 is mounted to a fixed member on a vehicle body. When the cable reel is mounted on the steering device, a steering wheel should be rotatable in opposite directions by substantially the same amount. This requirement can be met by providing a positioning mechanism between the movable member 1 and the fixed member 6 for properly positioning both members. The positioning mechanism comprises a gear 15 rotatably supported by a gear case 14 outwardly projecting from the outer ring wall 8 and a pair of projections 16 formed at the outer circumference of the movable member 1. When the movable member 1 is rotated 360 degrees, the projections 16 engage with the gear 15 to rotate the gear 15 by 90 degrees. Accordingly, by marking the gear case 14 and the gear 15 at suitable positions as an index, a relative position between the gear case 14 and the gear 15 may be made visible to thereby ensure proper positioning of the movable member 1 and the fixed member 6.
The operation of the above-described conventional cable reel is as set forth below.
In mounting the cable reel to the steering device, the movable member 1 and the fixed member 6 are properly positioned by using the positioning mechanism such that when the steering wheel is rotated in one direction, the flat cable 3 is wound around the inner ring wall 2 to a stroke end position; and when the steering wheel is rotated in the other direction, the flat cable 3 is unwound to the outer ring wall 8 until a stroke end position. In any case, the electrical connection between the movable member 1 (rotating part) and the fixed member 6 (fixed part) is maintained by the flat cable 3.
Even though the positioning mechanism is provided, there is a possibility that the cable reel will be erroneously mounted because an operator fails to notice the positioning marks, for example. If the cable reel is erroneously mounted in such a manner that the rotational amount of the movable member 1 in the unwinding direction of the flat cable 3 is too small, then when the steering wheel rotates movable member 1 in the unwinding direction by an amount greater than the predetermined unwinding amount, this results in the flat cable 3 being unwound and then rewound in the opposite direction, but the steering wheel is allowed to rotate. On the other hand, if the cable reel is erroneously mounted in such a manner that the available rotational amount of the movable member 1 in the winding direction of the flat cable 3 is too small, then when the steering wheel rotates movable member 1 in the winding direction by an amount equal to the available winding amount, the movable member 1 , and correspondingly the steering wheel, are locked by the flat cable 3, and further rotation thereof is restrained. To cope with this problem, the flat cable 3 is forcibly cut by the cutter 13 by applying a tension to the flat cable 3 (see FIG. 7), thereby preventing the locking of the movable member 1 and the steering wheel.
However, in the conventional cable reel as described above, the ring-like fixing member 11 is secured to the outer ring wall 8 of the fixed member 6 by, for example, a snap engaging means (not shown) to hold the outer circumferential end portion of the flat cable 3 to the fixed member 6. In view of the structure required to perform the above-described task, fixing member 11 is complicated to produce and makes assembly of the reel difficult. In addition, the cable reel is enlarged in size by the provision of the fixing member 1.